Wheat flooding and waterlogging

Flooding and waterlogging causes oxygen to rapidly deplete in the root zone. In turn, this oxygen deficiency affects several physiological processes such as water uptake, the uptake and transport of nutrients and root-shoot hormone relations.

How long wheat can survive

Wheat can probably handle three to four days of flooding and/or waterlogged soils before it negatively impacts grain yield, as long as some leaves are above water. Higher temperatures will hasten the depletion of oxygen and increase the risk of crop damage.

Deficiencies and yield losses

Acute nitrogen deficiencies are most commonly observed when the crop quickly yellows. The waterlogged soils impair nitrogen uptake, as well as increase the potential for denitrification and leaching. Extended periods of waterlogging reduce leaf elongation, kernel number and ultimately grain yield.

Photo 1: After three days of flooding near Crookston in 2002, adventitious roots became visible on the wheat stem’s first node.

Yield losses reported in scientific journals range between 20 to 50 percent when soils were waterlogged for more than 10 days. One study in winter wheat reported a yield loss of about 2 percent for each day soils were waterlogged. However, several studies have noted differences in waterlogging tolerance among wheat varieties.

Of varieties that handled waterlogging better, one of the characteristics researchers observed was the ability of varieties to initiate adventitious roots at the first node (Photo 1). When seminal roots are damaged or restricted, adventitious root growth is promoted. These may form the bulk of the functioning root system when soil is waterlogged for more than several days.